The Debian Tartan
Debian's tartan was created in the run-up to DebConf7 in 2007 which was about to be held in Edinburgh, Scotland.
To date (2015) about 280 yards of single-width cloth has been woven, in two batches, which was then made into about 30 kilts, as well as a few other garments including a Breacan Feile, skirts, trousers, a shawl, and 40 ties.
The tartan was originally registered in 2007 with the Scottish Tartans World Register (one of the three registrars available at the time). An act of the Scottish Parliament in 2008 then established The Scottish Register of Tartans, combining the pre-existing registries, so they now host the authoritative registration.
Below is a copy of the original Scottish Tartans World Register certificate, which also contains the source code, or "sett", of the tartan.
The colours seen on the registration page provide a reasonable match to the finished cloth (on my monitor, but monitors vary, so no guarantees there).
The size of that is such that the pattern will repeat about every 10 inches (with slight variation due to the vagaries of weaving).
When instructing a weaver, it's worth making sure that they get the cloth the right way round, so that when made into a kilt, the morse will read left-to-right and top-to-bottom, rather than bottom-to-top as it is in these images -- they got it right on the first run, but remember they're not used to having to worry about such things, so it's worth reminding them.
The copyright on the pattern resides with Hands.com Ltd., with the initial design being done by Philip Hands (i.e. the colour selection, and the morse code). Then some refinements were contributed by Geoffrey (Tailor), such as the placement of the Blue and Maroon, and the decision to make the pattern be symmetric on only one diagonal). Geoffrey (Tailor)'s copyright in the pattern has also been assigned to Hands.com Ltd.
I (Philip Hands) am happy to distribute it under the GPL and/or write to any weavers that question their right to use it, assuring them that they can for any purpose.
Notes about the tartan design:
It's predominantly red, to reflect the red from the logo, made of two shades of red to give a gradation towards the middle (the nearest thing I could get to a swirl in a plaid) the blue is "Electric Blue" which makes sense, since we wouldn't get far without electricity, and can be said to be a reference to Captain Blue Eye, there's a fair amount of black, and a little yellow, as a nod towards Tux, and the white spells out DEBIAN in morse (with a correct 1:3 ratio for dots to dashes, and for the pauses in and between letters).
Also, unusually (although not uniquely) for a tartan, it's not symmetric. The morse section does not repeat in reverse, so while it still looks like a fairly conventional tartan (if a little busy in the morse section) we don't get the reversed morse (which the designer helpfully pointed out would spell "ANIVEU" ;-). This means that the morse section can be made relatively larger without increasing the overall size of the sett.